Automatic casting method for small cross-section round billets

Abstract

The present application relates to the technical field of metallurgy, and particularly discloses an automatic casting method for small-section round billets. The automatic casting method for small-section round billets provided by the present application improves the control accuracy of subsequent automatic casting by precisely controlling the position of the stopper rod head, the accuracy of the stopper rod mechanism, and the method of sealing the ingot head, and automatically controls the flow of molten steel by controlling the opening degree of the stopper rod, so that the total breakout time of the molten steel is controlled to be 12s-20s, which not only ensures the strength and uniformity of the primary shell, but also prevents the problem of flow interruption of the molten steel in the nozzle, maintains the stability of the crystallizer liquid surface, and improves the success rate of automatic casting. At the same time, by controlling the pulling speed of the straightening machine, the stable control of the molten steel liquid surface is realized, the quality of the casting billet is improved, thereby effectively reducing the cutting waste amount of the casting billet, reducing the production cost, and having high popularization and application value.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, and in particular to an automatic casting method for small cross-section round billets. Background Technology

[0002] When casting begins in the tundish of a continuous casting machine, the tundish nozzle opens, and molten steel from the tundish is injected through the nozzle into the crystallizer containing the dummy ingot. The high-temperature molten steel splashes when it comes into contact with the room-temperature crystallizer and the dummy ingot head. As the molten steel fills the gap between the dummy ingot and the crystallizer and reaches a certain height within the crystallizer, the splashing decreases. The straightening machine then starts, slowly pulling out the dummy ingot and the billet solidified with the dummy ingot head. The pulling speed is then gradually increased until the set target pulling speed is reached. The above casting process, where the operator controls the opening of the tundish stopper and the pulling speed, is called manual casting. When the process is automatically controlled by a program, it is called automatic casting.

[0003] Small-section round billets are an important billet type in continuous casting and are currently widely used in continuous casting projects. Due to their small unit volume, small-section round billets have very high requirements for the fit between the stopper rod head and the nozzle bowl, the stopper rod opening degree, and the time of molten steel emergence. Therefore, manual casting is generally used in China. However, manual casting requires high operator skills and is prone to problems such as low casting success rate, high accident rate, and unstable billet quality. To compensate for the lack of operator skills, high superheat (≥45℃) methods are currently used for casting. However, this method easily causes severe secondary oxidation of molten steel, resulting in deterioration of the quality of the cast billets and an increase in the amount of scrap. Therefore, in order to improve production safety and efficiency, and to effectively improve the quality and pass rate of cast billets, it is necessary to develop an automatic casting method for small-section round billets. Summary of the Invention

[0004] To address the problems of unstable billet quality, high waste, low production efficiency, and poor operational safety associated with the existing manual casting method for small cross-section round billets, this invention provides an automatic casting method for small cross-section round billets.

[0005] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0006] An automated casting method for small-section round billets includes the following steps:

[0007] Step a: Adjust the mechanism precision of the tundish stopper rod, and control the center point of the stopper rod head to be biased towards the inner arc of the continuous casting machine and 2mm-3mm away from the center point of the tundish nozzle bowl;

[0008] Send the dummy bar into the crystallizer's pouring position and seal the gap between the top of the dummy bar and the crystallizer with threaded steel bars;

[0009] Step b: Turn on the baking machine to bake the tundish. After baking, align the submersible nozzle of the tundish car so that the submersible nozzle enters the crystallizer by 150mm-180mm. Then seal the stopper rod head with the nozzle bowl and inject molten steel into the tundish. When the molten steel level in the tundish is 350mm-450mm, add a covering agent. When the molten steel level in the tundish reaches the casting level, the automatic casting control process begins.

[0010] Step c: Immediately open the first stopper rod, with an opening of 12mm-15mm, for 1.5s-2.5s. Close the stopper rod for 2s-3s. Open the second stopper rod, with an opening of 5mm-6mm, for 4s-5s. Close the stopper rod for 1s-2s. Open the third stopper rod to stabilize the flow, with an opening of 5mm-6mm. When the molten steel level in the crystallizer is 200mm-220mm from the top of the copper tube in the crystallizer, enter PID automatic control, and the stopper rod will automatically control the flow.

[0011] Step d: When the molten steel level in the crystallizer is 80mm-100mm from the top of the copper tube in the crystallizer, the pulling speed of the straightening machine is increased to 0.6m / min-0.8m / min within 5s-7s, paused for 2s-3s, and then the pulling speed is increased to 0.9m / min-1.2m / min before switching to automatic control until the automatic casting is completed.

[0012] The diameter of the small cross-section round blank described in this invention is 160mm-250mm.

[0013] Compared to existing technologies, the automatic casting method for small-section round billets provided by this invention improves the control precision of subsequent automatic casting by precisely controlling the position of the stopper rod head, the accuracy of the stopper rod mechanism, and the sealing of the ingot head. Furthermore, by controlling the opening degree of the stopper rod to automatically control the flow of molten steel, the total emergence time of molten steel is controlled to 12-20 seconds. This ensures the strength and uniformity of the initial billet shell and prevents molten steel from being blocked in the nozzle, maintaining the stability of the crystallizer liquid level and improving the success rate of automatic casting. Simultaneously, by controlling the pulling speed of the straightening machine, stable control of the molten steel level is achieved, improving the quality of the cast billet and effectively reducing the amount of scrap cut during casting, thus lowering production costs. This invention achieves fully automatic casting by specifically controlling the process parameters in each step of the continuous casting process, solving the problems of high failure rate, low operational safety, and unstable billet quality associated with manual casting. It fills the gap in automatic casting technology for small-section round billets and has high application value.

[0014] Preferably, in step a, the precision of the mechanism for adjusting the intermediate packing stopper is specifically: controlling the gap between the rocker arm gear and the rack to be 0.2mm-0.3mm, and the swing of the front end of the crossbeam not exceeding 10mm.

[0015] By controlling the precision of the stopper rod mechanism and the specific position of the stopper rod center point, it is possible to ensure a good seal between the stopper rod and the nozzle bowl, avoiding the problem of molten steel flowing by itself. At the same time, it is also possible to ensure that the stopper rod opening deviation is within ±0.5mm during subsequent pouring, thereby improving the control precision of the stopper rod.

[0016] Preferably, in step a, the pouring position is: the top of the ingot head is inserted 290mm-310mm into the lower opening of the crystallizer.

[0017] The optimal pouring location can prevent molten steel from splashing onto the top of the crystallizer and causing cold steel problems during pouring.

[0018] Preferably, in step a, the amount of threaded steel bar used is 18kg-30kg.

[0019] Furthermore, the diameter of the threaded steel bar is 16-20mm.

[0020] Using the above-mentioned amount of threaded steel bars for sealing the ingot can ensure sufficient billet shell thickness and avoid the billet head being too hard, which could cause jamming problems.

[0021] Preferably, in step b, the baking time of the intermediate bread is 4-5 hours, and the temperature of the intermediate bread is 1100℃-1250℃.

[0022] Preferably, in step b, the amount of the covering agent added is 300kg-350kg.

[0023] Preferably, in step b, the temperature of the molten steel injected into the tundish is 1580℃-1610℃.

[0024] Preferably, in step b, the liquid level height of the pouring surface is 500mm-600mm.

[0025] Preferably, in step c, when the molten steel in the crystallizer rises to a position 200mm-220mm away from the top of the copper tube of the crystallizer, the straightening machine is started. The starting speed of the straightening machine is 0.3m / min-0.5m / min, and it is stabilized for 1s-2s.

[0026] The preferred stopper rod control method can control the total emergence time of molten steel to 12s-20s, which not only ensures the strength and uniformity of the initial billet shell, but also prevents the molten steel from being blocked in the nozzle, maintains the stability of the liquid surface in the crystallizer, and improves the success rate of automatic casting.

[0027] Preferably, the diameter of the stopper rod is 120mm-140mm.

[0028] Preferably, in step d, the pulling speed is increased to 0.9m / min-1.2m / min within 3s-5s.

[0029] The preferred casting speed control method can avoid problems such as billet pull-out or steel leakage, which is conducive to improving the quality of the first casting billet, reducing the amount of scrap cut from the first casting billet, and lowering production costs.

[0030] The automatic casting method for small cross-section round billets provided by this invention achieves automatic casting of small cross-section round billets through precise control and coordination of all continuous casting process steps. It has a high success rate in casting, improves the quality and production continuity of small cross-section round billets, increases production efficiency, and reduces production costs. It is of great significance for improving the competitiveness of enterprises and has broad market prospects. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0032] To better illustrate the present invention, further examples are provided below.

[0033] Example 1

[0034] This invention provides an automatic casting method for small-section round billets, comprising the following steps:

[0035] Adjust the stopper rod mechanism precision, control the gap between the rocker arm gear and the rack to be 0.2mm, and the swing of the front end of the crossbeam should not exceed 10mm; when installing the stopper rod in the tundish, control the center point of the stopper rod head to be close to the center point of the nozzle bowl in the inner arc direction of the continuous casting machine; insert the top of the dummy bar head into the bottom of the crystallizer 300mm, and seal the gap between the top of the dummy bar head and the crystallizer with threaded steel bars. The amount of threaded steel bars (diameter φ18mm) used is 18kg-19kg;

[0036] Turn on the baking machine to bake the tundish for 4 hours. The baking temperature of the tundish working layer is 1130℃. After baking, move the tundish car to the pouring position, align the submerged entry nozzle, and lower the tundish car so that the submerged entry nozzle enters the crystallizer 180mm. Then, gently lift the stopper rod handle to seal the stopper rod head with the nozzle cup. Connect the stopper rod electric cylinder cable and press the empty button to clear the false liquid level in the liquid crystal. Turn on the driver power and switch to automatic mode. Pour molten steel at 1580℃ into the tundish. When the molten steel level in the tundish is 400mm, add the covering agent. When the molten steel level in the tundish reaches 550mm, press the automatic pouring button to start the automatic pouring process.

[0037] Immediately open the first stopper rod to an opening of 15mm for 1.5s, then close the stopper rod for 2s, open the second stopper rod to an opening of 5mm for 4s, close the stopper rod again for 1s, and finally open the third stopper rod to stabilize the flow with an opening of 5mm. The second stopper rod is used to jog and fine-tune the stopper rod opening to control the steel flow rate once (jog 1mm / time).

[0038] When the molten steel in the crystallizer rises to 240mm from the top of the copper tube of the crystallizer, the vibration is automatically started; when the molten steel in the crystallizer rises to 220mm from the top of the copper tube of the crystallizer, the straightening machine is automatically started and enters the PID automatic control state. The stopper rod is automatically controlled to follow the flow. The starting speed of the straightening machine is 0.4m / min and it stabilizes for 1s.

[0039] When the molten steel level in the crystallizer is 90mm from the top of the copper tube in the crystallizer, the tensioning speed of the straightening machine is increased to 0.7m / min within 6s, paused for 2s, and then increased to 1.1m / min within 4s before switching to automatic control until the automatic casting is completed.

[0040] Example 2

[0041] This invention provides an automatic casting method for small-section round billets, comprising the following steps:

[0042] Adjust the stopper rod mechanism precision, control the gap between the rocker arm gear and the rack to be 0.3mm, and the swing of the front end of the crossbeam to not exceed 10mm; when installing the stopper rod in the tundish, control the center point of the stopper rod head to be close to the center point of the nozzle bowl in the inner arc direction of the continuous casting machine by 2mm; insert the top of the dummy bar head into the bottom opening of the crystallizer by 310mm, and seal the gap between the top of the dummy bar head and the crystallizer with threaded steel bars. The amount of threaded steel bars (diameter φ18mm) used is 20kg-21kg;

[0043] Turn on the baking machine to bake the tundish for 4.5 hours. The baking temperature of the tundish working layer is 1200℃. After baking, move the tundish car to the pouring position, align the submersible nozzle, and lower the tundish car so that the submersible nozzle enters the crystallizer 150mm. Then, gently lift the stopper rod handle to seal the stopper rod head with the nozzle cup. Connect the stopper rod electric cylinder cable, press the empty button to clear the false liquid level in the liquid crystal. Turn on the driver power, switch to automatic mode, and pour molten steel at 1590℃ into the tundish. When the molten steel level in the tundish reaches 350mm, add the covering agent. When the molten steel level in the tundish reaches 600mm, press the automatic pouring button to start the automatic pouring process.

[0044] The stopper rod immediately opens the first rod to an opening of 12mm for 2.5s, then closes the stopper rod for 3s, opens the second rod to an opening of 6mm for 4s, closes the stopper rod again for 2s, and finally opens the third rod to stabilize the flow to an opening of 6mm. The second rod is used to jog and fine-tune the stopper rod opening to control the steel flow rate once (jog 1mm / time).

[0045] When the molten steel in the crystallizer rises to 240mm from the top of the copper tube of the crystallizer, the vibration is automatically started; when the molten steel in the crystallizer rises to 210mm from the top of the copper tube of the crystallizer, the straightening machine is automatically started and enters the PID automatic control state. The stopper rod is automatically controlled to follow the flow. The starting speed of the straightening machine is 0.3m / min and it stabilizes for 1s.

[0046] When the molten steel level in the crystallizer is 80mm from the top of the copper tube in the crystallizer, the tensioning speed of the straightening machine is increased to 0.6m / min within 5s, paused for 2s, and then increased to 0.9m / min within 3s before switching to automatic control until the automatic casting is completed.

[0047] Example 3

[0048] This invention provides an automatic casting method for small-section round billets, comprising the following steps:

[0049] Adjust the stopper rod mechanism precision, control the gap between the rocker arm gear and rack to be 0.2mm, and the swing of the front end of the crossbeam to not exceed 10mm; when installing the stopper rod in the tundish, control the center point of the stopper rod head to be close to the center point of the nozzle bowl in the inner arc direction of the continuous casting machine by 3mm; insert the top of the dummy bar head into the lower opening of the crystallizer by 290mm, and seal the gap between the top of the dummy bar head and the crystallizer with threaded steel bars. The amount of threaded steel bars (diameter φ20mm) used is 27kg-28kg;

[0050] Turn on the baking machine to bake the tundish for 4.7 hours. The baking temperature of the tundish working layer is 1200℃. After baking, move the tundish car to the pouring position, align the submersible nozzle, and lower the tundish car so that the submersible nozzle enters the crystallizer 165mm. Then, gently lift the stopper rod handle to seal the stopper rod head with the nozzle cup. Connect the stopper rod electric cylinder cable, press the empty button to clear the false liquid level in the liquid crystal. Turn on the driver power, switch to automatic mode, and pour molten steel at 1600℃ into the tundish. When the molten steel level in the tundish reaches 450mm, add the covering agent. When the molten steel level in the tundish reaches 500mm, press the automatic pouring button to start the automatic pouring process.

[0051] Immediately open the first stopper rod to an opening of 13mm for 2s, then close the stopper rod for 2s, open the second stopper rod to an opening of 5mm for 4s, close the stopper rod again for 1s, and finally open the third stopper rod to stabilize the flow with an opening of 5mm. The second stopper rod is used to jog and fine-tune the stopper rod opening to control the steel flow rate once (jog 1mm / time).

[0052] When the molten steel in the crystallizer rises to 240mm from the top of the copper tube of the crystallizer, the vibration is automatically started; when the molten steel in the crystallizer rises to 200mm from the top of the copper tube of the crystallizer, the straightening machine is automatically started and enters the PID automatic control state. The stopper rod is automatically controlled to follow the flow. The starting speed of the straightening machine is 0.5m / min and stabilizes for 2s.

[0053] When the molten steel level in the crystallizer is 100mm from the top of the copper tube in the crystallizer, the tensioning speed of the straightening machine is increased to 0.8m / min within 7s, paused for 3s, and then increased to 1.2m / min within 5s before switching to automatic control until the automatic casting is completed.

[0054] Comparative Example 1

[0055] This comparative example provides a manual casting method for small-section round billets, which specifically includes the following steps:

[0056] When installing the tundish stopper rod, control the center point of the stopper rod head to be 3mm away from the center point of the nozzle bowl in the inner arc direction of the continuous casting machine; insert the top of the dummy bar into the bottom of the crystallizer 300mm, and seal the gap between the top of the dummy bar and the crystallizer with threaded steel bars. The amount of threaded steel bars (diameter φ18mm) used is 18kg-19kg.

[0057] Turn on the baking machine to bake the tundish for 4.5 hours. The baking temperature of the tundish working layer is 1200℃. After baking, move the tundish car to the pouring position, align the submersible nozzle, and lower the tundish car so that the submersible nozzle enters the crystallizer 180mm. Then, gently lift the stopper rod handle to seal the stopper rod head with the nozzle cup. Insert the stopper rod electric cylinder cable, press the empty button, and clear the false liquid level in the crystallizer. Pour molten steel at 1580℃ into the tundish. When the molten steel level in the tundish is 400mm, add the covering agent. When the molten steel level in the tundish reaches 550mm, manually start pouring, opening and closing the stopper rod 2-3 times (fully open and fully close).

[0058] When the molten steel in the crystallizer rises to 150-250mm from the top of the copper tube of the crystallizer, start the crystallizer vibration and straightening machine. Manually increase the pulling speed to 1.1m / min within 5-10 seconds. When the molten steel level in the crystallizer is 90mm from the top of the steel tube of the crystallizer, enter PID automatic control until the casting is completed.

[0059] The diameter of the stopper rod used in Examples 1-3 and Comparative Example 1 was 130 mm.

[0060] After slow cooling, the surface quality of the cast billets obtained in Example 1 and Comparative Example 1 was inspected. The billet head of Comparative Example 1 needed to be cut off by 3.8m to meet the quality standard requirements, while the billet head of Example 1 needed to be cut off by 2.2m to meet the quality standard requirements.

[0061] The casting billets prepared in Example 1 and Comparative Example 1 were subjected to low-magnification rating and inclusion inspection according to standards YB / T 4149-2018 and GB / T 10561-2005. The inspection results are shown in Table 1.

[0062] Table 1

[0063] Low-density loose / grade Low magnification shrinkage / grade Total number of inclusions / level Example 1 1.0 0 1.5 Comparative Example 1 1.5 0 2.0

[0064] As can be seen from the above comparison, the automatic casting method for small cross-section round billets provided in the embodiments of the present invention can effectively reduce the amount of billet cutting loss, increase the steel billet yield, improve the quality of continuously cast billets, and reduce production costs, thus having high practical value.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for automatic start of casting of a small cross-section round billet, characterized in that, The method comprises the following steps: Step a, adjusting the mechanism accuracy of the tundish stopper, controlling the center point of the stopper head to deviate from the inner arc of the continuous caster and to be 2-3 mm away from the center point of the tundish nozzle bowl; The dummy bar is sent to the casting position of the crystallizer, and a threaded steel bar is used to block the gap between the top of the dummy head and the crystallizer; Step b, turning on the roaster to bake the tundish, and after the baking is completed, the submerged nozzle of the tundish car is centered so that the submerged nozzle enters the crystallizer by 150-180 mm, then the stopper head is sealed with the nozzle bowl, the molten steel is injected into the tundish, and when the liquid level of the molten steel in the tundish is 350-450 mm, a covering agent is added; when the liquid level of the molten steel in the tundish reaches the casting liquid level, the automatic casting control process is entered; Step c, immediately open the first rod, the stopper opening is 12-15 mm, the duration is 1.5-2.5 s, the stopper is closed for 2-3 s, the second rod is opened, the stopper opening is 5-6 mm, the duration is 4-5 s, the stopper is closed for 1-2 s, the third rod is opened for flow stabilization, and the stopper opening is 5-6 mm; when the liquid level of the molten steel in the crystallizer is 200-220 mm away from the upper opening of the copper pipe of the crystallizer, the PID automatic control is entered, and the stopper is automatically controlled to follow the flow; Step d, when the liquid level of the molten steel in the crystallizer is 80-100 mm away from the upper opening of the copper pipe of the crystallizer, the casting speed of the withdrawal and straightening machine is increased to 0.6-0.8 m / min within 5-7 s, paused for 2-3 s, then increased to 0.9-1.2 m / min, and automatically controlled until the automatic casting is completed.

2. A method of automatically starting a small cross-section round billet as claimed in claim 1, wherein In step a, the mechanism accuracy of the tundish stopper is adjusted by controlling the gap between the rocker gear and the rack to be 0.2-0.3 mm, and the swing of the front end of the cross beam is not more than 10 mm.

3. The automatic start-up method of a small cross-section round billet according to claim 1, wherein In step a, the casting position is that the top of the dummy head is inserted into the lower opening of the crystallizer by 290-310 mm.

4. The automatic start-up method of a small- section round billet according to claim 1, wherein In step a, the amount of the threaded steel bar used is 18-30 kg.

5. The automatic start-up method of a small- cross-section round billet according to claim 1, wherein In step b, the baking time of the tundish is 4-5 h, and the temperature of the tundish is 1100-1250℃.

6. The automatic start-up method of a small- section round billet according to claim 1, wherein In step b, the amount of the covering agent added is 300-350 kg.

7. The automatic start-up method of a small-extrusion-round-billet according to claim 1, wherein In step b, the temperature of the molten steel injected into the tundish is 1580-1610℃.

8. The automatic start-up method of a small- cross-section round billet according to claim 1, wherein In step b, the liquid level of the casting liquid level is 500-600 mm.

9. The automatic start-up method of a small-extrusion-round-billet according to claim 1, wherein In step c, when the molten steel in the crystallizer rises to 230-250 mm away from the upper opening of the copper pipe of the crystallizer, the vibration is started; when the molten steel in the crystallizer rises to 200-220 mm away from the upper opening of the copper pipe of the crystallizer, the withdrawal and straightening machine is started, and the starting casting speed of the withdrawal and straightening machine is 0.3-0.5 m / min, and is stabilized for 1-2 s.

10. The automatic start-up method of a small- cross-section round billet according to claim 1, wherein In step d, the casting speed is increased to 0.9-1.2 m / min within 3-5 s.